We will be completing the sequence analysis of alpha-GPDH from Drosophila melanogaster and then will survey a number of wild genomes for sequence variation. This will then be extended to Drosophila pseudoobscura. A second aspect of the work is the completion of the survey of Esterase-5 and xanthine dehydrogenase proteins in a very large sample of isogenic lines from three natural populations. The survey was the multi-pass method of electrophoresis involving changes in pH and gel concentration which identifies virtually all variants. It will then be possible to test various hypothesis about the maintenance of the variation.